Control device



J. L. HARRIS CONTROL DEVICE June 2, 1964 Filed March 28, 1962 JMvwk/orl fa 4 A FINAL RESE T United States Patent 3,135,908 CONTROL DEVICE John L. Harris, 4753 N. Newhall St., Milwaukee, Wis. Filed Mar. 28, 1962, Ser. No. 183,194 7 Claims. (Cl. 318-476) This invention relates in general to automatic controls and more particularly to timing controls for use with air conditioners and other types of refrigeration systems.

In compression type refrigeration systems a substantial pressure differential is developed by the compressor when it runs. 'When the compressor is stopped, this pressure differential equalizes in a short period of time so that it is relatively easy to start the compressor for the next cycle. However, if the compressor is started before this equalization takes place an excessive starting torque is required.

One object of the invention is to provide a unitary control device which can be interposed between the compressor and its automatic control such as a thermostat and which insures that the compressor cannot be started until the predetermined time has elapsed after stopping the compressor.

A further object of the invention is to provide a unitary control device which delays the starting of a compressor for a short time after the thermostat or other condition responsive device calls for cooling.

Another object of the invention is to provide a combination timer and electric magnetic control in which power from the timer motor is used for equalizing the pull-in and drop-out characteristics of the electromagnet.

Other objects will appear from the following description and appended claims.

For a full disclosure of the invention reference is made to the following detailed description and to the accompanying drawings in which:

FIG. 1 is a front elevation of the new control device with a portion of the case removed to shown the working mechanism.

FIG. 2 is a side view of FIG. 1.

FIG. 3 is an enlarged view of the cam shaft assembly.

FIGS. 4, 5 and 6 show the switch and cam follower locations assumed during different portions of the operating cycle. 1

FIG. 7 is a schematic Wiring diagram of a typical installation.

Referring to FIGS. 1 and 2, the mechanism is mounted in a housing including a back plate 1 and a front plate 2 which supports a switch panel 3. This switch panel supports a switching mechanism consisting of flexible switch blades 4, 5 and 6 carrying contacts 7, 8 and 9 respectively. The switch also includes a stationary contact bracket 10 carrying a contact 11. The switch blades 4, 5 and 6 are of unequal lengths. Thus, blade 5 is slightly longer than blade 4, and blade 6 in turn is slightly longer than blade 5. All of the switch blades are biased downwardly as seen in FIG. 1.

The switch blades 4, 5 and 6 are operated by means of a pair of cam followers 12 and 13 which are supported side by side on a shaft 14 which extends between the back and front plates 1 and 2. The cam follower 12 is made of insulation material and is staked to a cam follower bearing 15 which is loosely carried on shaft 14. The cam follower 13 is also made of insulation material and is attached to a bearing 16 also carried on shaft 14.

Both cam followers 12 and 13 ride upon a cam 18 which is carried on a cam shaft 19 also extending between plates 1 and 2. This cam shaft 19 carries a gear 20 which is driven by a timer motor 21 through suitable intermediate gearing. As shown in FIG. 3, the gear 20 is carried on a hub 22 which is pressed on shaft 3,135,908 Patented June 2, 1964 19. Also a tension washer 23 is interposed between the gear and shaft so as to provide a friction clutch between gear 20 and shaft 19. This permits the shaft 19 to be manually turned by a screw driver for testing out the system.

Also mounted on the plate 1 is a solenoid 25 of usual construction having a coil and a plunger 26. This solenoid plunger is pivotally attached to a bell crank lever 27 carried by a shaft 28 which extends between plates 1 and 2. A torsion spring 30 is carried by the shaft 28. One leg of this spring bears against the side of the case and the other leg of the spring bears on the pin 31 which attaches the bell crank 27 to the solenoid plunger. The spring 30 thus serves to bias the solenoid plunger 26 downwardly, and to bias lever 27 in a counterclockwise direction.

The cam follower 12 in addition to being controlled by the cam 18 is also actuated by the bell crank lever 27. This actuation is performed by a pin 32 which is carried by the bell crank 27 and which extends into a hole 33 in the cam follower 12. The bell crank 27 in addition to being actuated by the solenoid plunger 26 is also actuated by a cam 35 which is carried 'by the cam shaft 19. This cam 35 is loosely carried on the shaft 19 and is driven by a pin 36 which is carried by the cam 18 which in turn is pressed over knurls on shaft 19. A torsion spring 37 is carried by the shaft 19 and located between cams 18 and 35. One end of this spring bears against the pin 36 and the other end is formed to fit behind the cam 35. This spring biases the cam 35 in a counter-clockwise direction relative to earn 18 as seen in FIG. 1.

Referring to FIG. 7, the compressor 40 is controlled by a contactor or motor starter having a coil 41 and switches 42 and 43. This motor starter is controlled by a thermostat 44 through contacts 7 and 11 of the switching mechanism.

Operation The parts in FIGS. 1 and 7 are shown in the standby. positions where the control unit is awaiting a call from cooling from the thermostat to start the compressor. At this time contacts 7 and 8 are engaged so that the thermostat 44 is in circuit with the timer motor 21. C011- tacts 7 and 11 are open which prevents the thermostat from energizing the contactor coil 41 or the timer solenoid 25.

Referring in particular to FIG. 1, the cam follower 12 has dropped off the cam 18. However, cam follower 13 is slightly longer than the cam follower 12 and this cam follower 13 is still riding the top of the cam 18.

In this standby position, the cam 35 has been driven by the pin 36 and has lifted the horizontal portion of the bell crank 27 to a point where the solenoid plunger 26 is almost at the upper limit of its range of movement. At this time the spring 37 has been compressed as its torque is insufficient to drive the cam 35 against the load imposed by the cam follower portion of the bell crank 27.

It will be noted that cam follower 12 at this time is not engaged with any of the switch blades. However, the rear cam follower 13 which is still riding the cam 18 has portions which engage the switch blades 4 and 6. This has lifted the blade 4 to the point at which the contacts 7 and 8 are engaged. This follower 13 has also lifted the switch blade 6 so that contacts 8 and 9 are separated.

When the thermostat calls for cooling it energizes the timer motor 21. This timer motor starts running and rotates the cam shaft 19 in a counter-clockwise direction as seen in FIG. 1. In approximately fifteen seconds the cam follower 13 drops off the cam 18 and the switch blades now energized position.

assume the positions shown in FIG. 4. The cam follower 13) in dropping off cam 18 rotated in a counter-clockwise direction. This released blade 4 thus allowing contacts 7 and 11 to close. During this dropping off movement of cam follower 1.3, the switch blade 5 followed switch blade 4 downwardly until it engaged the cam follower 12 which now holds blade 5 in an intermediate position in which the contacts 7 and 8 are separated. The switch blade 6 also moved downwardly with this counter-clockwise rotation of the cam follower 13. However, this motion was not suflicient to entirely close the gap between contacts 8 and 9 so that these contacts are still separated.

The parts are now in the run position. Opening of contacts '7 and 8 stopped the timer motor. Closing of contacts '7 and 11 energized the contactor coil 41, thus starting the compressor 49. This also simultaneously energized the solenoid 25 in the timer. This caused upward movement of the solenoid plunger 26 to the upper limit of its stroke and thus caused the bell crank lever 27 to disengage the cam 35. This removed the holding force which prevented the spring 37 from rotating the cam 35. As a result the spring 36 now causes rotation of the cam 35 in a counter-clockwise direction, so that it clears the cam follower section of the bell crank 27.

The parts now remain in this position and the compressor operates until the thermostat becomes satisfied. When this happens, the thermostat opens its circuit and thus de-energizes both the timer solenoid and the contactor coil 41. The compressor thus stops. Inasmuch as the cam 35 is no longer under the bell crank 27, de-energization of the solenoid coil permits the biasing spring 30 to rotate the bell crank 27 in a counter-clockwise direction as seen in FIG. 1. The pin 32 in the bell crank now engages the right side of the hole 33 in cam follower 12 and rotates the cam follower 12 in a clockwise direction as seen in FIG. 1. The parts now assume the positions shown in FIG. 5. It will be noted that the cam follower 12 has lifted the blade 4 so as to break contacts '7 and 11. It has also lifted the blade 5 to cause engageintent of contacts 8 and 9. Due to contacts 7 and 11 now being opened, the thermostat is disconnected from the contactor coil 41. Thus the coil 41 would remain de-energized even if the thermostat should immediately call for cooling. Inasmuch as the timer solenoid 25 is also connected through timer contacts 7 and 11, the opening of these contacts prevents the thermostat from energizing the timer solenoid at this time.

The timer motor now runs, rotating the cam shaft in the counter-clockwise direction as seen in FIG. 1. During this motion the cam 35 remains stationary until after the lost motion between it and the pin 36 is taken up. During this movement the spring 37 is rewound for the next cycle. As the cams rotate, the bell crank 27 remains stationary until after the cam 18 has come under the cam follower 12. After this has taken place, the bell crank 27 is cammed in a clockwise direction and thus the pin 32 is shifted to the left so as to free the cam followerlZ for dropping off" its cam 18. During this same movement the cam 18 comes under the cam follower 13 and thus the parts have assumed the positions shown in FIG. 6.

After a suitable delay such as five minutes, the cam follower 12 drops olf the cam 18 and the parts reassume the standby position shown in FIG. 1.

From the foregoing description it will be noted that the load switch 711 can be closed only by the timer. This switch is opened instantly by the solenoid 25 dropping out :in response to the thermostat becoming satisfied. Once the switch is opened in this manner the solenoid is rendered incapable of reclosing the switch and it can close again only after the timer has run through its delay cycle.

It will be noted that the earn 35 utilizes power from the timer motor to move the solenoid almost back to its t this time the cam and bell crank 27 act as a holding means for maintaining the solenoid plunger in this almost energized position. When the solenoid is energized the cam 35 moves out from under lever 27 due to the action of spring 37. This, in effect, releases the holding means so that the solenoid is free to drop out when it is de-energized.

This arrangement, in which the solenoid is moved almost to its energized position by the timer motor decreases the amount of work which the solenoid must do. Thus a comparatively small solenoid can be used. Also, this arrangement brings the pull-in and drop-out voltages of the solenoid close together and permits the solenoid to also serve as a low voltageprotector.

From the foregoing it will be apparent that the invention interposes a positive delay between the time the compressor stops and the time that it can be restarted. It will also be seen that the invention interposes a delay between the time the thermostat calls for cooling and the time the compressor is started. This feature prevents false starts of the compressor due to vibration, etc., of the thermostat.

While the invention has been shown and described in connection with an air conditioning or refrigeration control system, it will be obvious that certain features of the invention are of broader scope and can be used in other applications.

While a preferred form of the invention has been shown and described it will be apparent that many changes can be made without departing from the spirit and scope of the invention. It is therefore desired to be limited only by the scope of the appended claims.

I claim:

1. In a control system for a condition changing system including a compressor, a condition responsive means for controlling said compressor, a switch interposed between said condition responsive means and said compressor, means including a timer motor and a solenoid mechanically and conjointly operating said switch, said solenoid being controlled by said condition responsive means and being arranged to open said switch when the condition responsive means stops the compressor, means actuated by said solenoid when opening said switch for starting said timer motor, and means actuated by said timer motor for reclosing said switch after said timer motor has run for a predetermined time.

2. In a control system for a condition changing system including a compressor, a condition responsive means for controlling said compressor, a switch interposed between said condition responsive means and said compressor, means including a timer motor and a solenoid for mechanically and conjointly operating said switch, said solenoid being controlled by said condition responsive means and being arranged to open said switch when the condition responsive means stops the compressor, means actuated by said solenoid when opening said switch for starting said timer motor independently of said condition responsive means, means for placing said timer motor under the control of the condition responsive means after a predetermined time, and means actuated by the timer motor after it has run for a predetermined time under the control of said condition responsive means for reclosing said switch.

3. In a control system for a condition changing system including a condition changer and a condition responsive device for controlling said condition changer, a control device interposed between said condition responsive device and condition changer, said control device including a solenoid, a time motor, and a switch mechanism having two outer contacts and two movable inner contacts, one outer contact being connected to the condition changer and the adjacent inner contact connected to the condition responsive device, the other inner contact being connected to the timer motor and the other outer contact being connected to a power service, and means operated conjointly by the timer motor and solenoid for actuating said two movable inner contacts.

4. In a control system for a condition changing system including a condition changer and a condition responsive device for controlling said condition changer, a control device having a switch interposed between said condition responsive device and said condition changer, said control device including an electro-magnet having a coil,

and a movable member arranged to move in a first direction When the coil is energized, said coil being controlled by the condition responsive device and said movable member being arranged to open said switch upon deenergization of said coil, a timer arranged to reclose said switch, means actuated by said movable member for starting said timer, means actuated by said timer for moving said movable member in said first direction, means for holding said movable member in a predetermined position, and means actuated by further movement of the movable member by energization of said coil for releasing said, holding means.

5. In an automatic control, a switch, a timer arranged to operate said switch in one direction, an electro-magnet having a coil and a movable member arranged to move in a first direction when the coil is energized, said movable member being arranged to operate said switch in the opposite direction when said movable member moves in a direction opposite to said first direction, said timer being arranged to move said movable member in said first direction independently ofsaid coil to a predetermined position, means for holding said movable memher in said predetermined position, and means actuated by further movement of said movable member by said coil for releasing said holding means.

6. In a timing control, an electric timer motor, a control deviceactuated by said timer motor, an electromagnet having a coil and a movable member arranged to move in a first direction when the coil is energized, means operated by the timer motor for moving said mov able member in said first direction, holding means for holding said movable member in a predetermined position, and means actuated upon further movement of said movable memberby energization of said coil for releasing said holding means.

7. In an automatic control, an electro-magnet having a coil and a movable member arranged to move in a first direction when said coil is energized, biasing means for biasing said movable member in the opposite direction, a control device actuated by said movable member, means independent of said coil for moving said movable'mernher in said first direction and for holding said movable member in a predetermined position, and means actuated upon further movement of said movable member by energization of said coil for releasing said holding means.

References Cited inthe file of this patent UNITED STATES PATENTS 

1. IN A CONTROL SYSTEM FOR A CONDITION CHANGING SYSTEM INCLUDING A COMPRESSOR, A CONDITION RESPONSIVE MEANS FOR CONTROLLING SAID COMPRESSOR, A SWITCH INTERPOSED BEBETWEEN SAID CONDITION RESPONSIVE MEANS AND SAID COMPRESSOR, MEANS INCLUDING A TIMER MOTOR AND A SOLENOID MECHANICALLY AND CONJOINTLY OPERATING SAID SWITCH, SAID SOLENOID BEING CONTROLLED BY SAID CONDITION RESPONSIVE MEANS AND BEING ARRANGED TO OPEN SAID SWITCH WHEN THE CONDITION RESPONSIVE MEANS STOPS THE COMPRESSOR, MEANS ACTUATED BY SAID SOLENOID WHEN OPENING SAID SWITCH FOR STARTING SAID TIMER MOTOR, AND MEANS ACTUATED BY SAID 